1. Field of the Invention
The present invention relates to an inkjet printer which performs printing by ejecting ink onto a print medium.
2. Description of the Related Art
Line-type inkjet printers have been known which performs printing by ejecting ink from a fixed inkjet head onto a sheet of paper while transporting the sheet of paper.
Some of such line-type inkjet printers include an inkjet head having an ink chamber partitioned into two regions and two nozzle rows configured to eject ink stored in the regions, respectively. The nozzle positions in one of the two nozzle rows are shifted from those in the other nozzle row in a main scanning direction by half of the nozzle pitch (half-pitch).
With such an inkjet head, two colors of ink can be ejected from one inkjet head. Alternatively, in the case where ink of the same color is ejected from the two nozzle rows, the printing resolution for that color can be improved.
In some inkjet printers, to maintain appropriate ink temperature during printing, the ink temperature is adjusted in an ink feed system (for example, see Japanese Patent Application Publication No. 2003-220714 (Patent Document 1)).
In inkjet heads, when an ink ejection operation is performed, the ink temperature in the inkjet head is increased by heat generated by components such as piezoelectric elements which cause the nozzles to eject ink.
In the case where the aforementioned inkjet head causes the two nozzle rows to eject ink of the same color distributed and fed through a common conduit, a difference between the operating rates of the two nozzle rows may cause an ink temperature difference between regions in the inkjet head which correspond to the nozzle rows. Further, as continuous printing time increases, the temperature difference may increase, and ink for one of the nozzle rows may deviate from a proper temperature range early. This may reduce the time during which printing can be performed at ink temperatures within the proper temperature range. The deviation of ink temperature from the proper temperature range results in, for example, unstable flight of ink, which causes degradation in print quality.
Adjusting ink temperature in the ink supply system as described in Patent Document 1 cannot alleviate the above-described ink temperature difference in the inkjet head.